1. Technical Field
The present invention relates to a solid oxide fuel cell (“SOFC” below) device, and more particularly to a solid oxide fuel cell device for generating power by reacting fuel gas with air.
2. Description of the Related Art
Solid oxide fuel cell (SOFC) device operates at relatively high temperatures, using an oxide ion-conducting solid electrolyte as an electrolyte, with electrodes placed on each side thereof, and with fuel gas supplied to one side thereof and oxidant (air, oxygen, or the like) supplied to the other side thereof.
In such SOFC device, steam or CO2 is produced by the reaction between oxygen ions passed through the oxide ion-conducting solid electrolyte and fuel, thereby generating power and thermal energy. The electrical power is removed from the SOFC device, where it is used for various electrical purposes. The thermal energy is transferred to the fuel, the SOFC device, the oxidant, and the like, and is used to raise the temperature thereof.
In conventional SOFC, the power generating chamber is disposed beneath a sealed space within the fuel cell module, and a fuel cell assembly furnished with multiple fuel cells is disposed within this generating chamber. A combustion chamber is formed above this fuel cell assembly; residual fuel gas and oxidant gas (air) combust directly in the upper portion itself of the fuel cell assembly, and exhaust gas is produced within the combustion chamber.
A reformer for reforming fuel gas into hydrogen is disposed at the top of the combustion chamber, and the reformer is heated by the heat of combustion within the combustion chamber to a temperature sufficient to perform reforming.
However, in conventional SOFC device of this type, other than directly combusting the residual fuel gas and oxidant gas at the top portion itself of the fuel cell assembly, no heating means such as a burner was provided to separately heat the combustion chamber or the reformer, or to ignite fuel gas at the upper portion of the fuel cell assembly during cold starts in order to start the fuel cell module at essentially the outside temperature or a temperature below the outside temperature, or to support the prevention of flameout or blow out after ignition, and so forth. It was therefore extremely difficult to perform reliable uniform ignition over the entirety of the multiple fuel cells which may exceed 100 in number, due to formation defects in the ignition portion caused by variability in the structure of the cell itself, and in particular, the effects of unstable airflows within the combustion chamber when cold starting the fuel cell module at a temperature which is essentially equal to or below the outside temperature; even if ignition occurs, flameout can occur due to the slightest turbulence in air flow and the like, making it extremely difficult to achieve a stable ignition or maintain an ignited state.
To counter ignition deficiencies of this type, it has been proposed in Japanese Patent Unexamined Publication No. 2008-135268 (JP-2008-135268A) and the like that such ignition problems caused by air flow could be countered by reducing the supply flow rate of the air which threatens to blow out the flame when the fuel cell ignites.